We were using a precondition which crashes the program when invalid input is
provided. We want to provide a way to gracefully check and handle invalid input
or shutdown the program if necessary.
SR-1930
There's still work left to do. In terms of next steps, there's still rdar://problem/22126141, which covers removing the 'workaround' overloads for print (that prevent bogus overload resolution failures), as well as providing a decent diagnostic when users invoke print with 'appendNewline'.
Swift SVN r30976
This consolidates the \x, \u, and \U escape sequences into one \u{abc} escape sequence.
For now we still parse and cleanly reject the old forms with a nice error message, this
will eventually be removed in a later beta (tracked by rdar://17527814)
Swift SVN r19435
